carburators

[86stepside]

I have a bb 402 with q-jet was hesitating off idle and sputtering a falling on its face at about 4500 rpms bought a jet perfomance q-jet . still does same thing . new plugs,wires,rotor and cap still does same thing

 

[gpmorgan]

Welcome to the forum RJ. It sounds fuel related. Might try a fuel pump. Do you get any backfires from the engine?

 

[86stepside]

all new fuel lines 3/8 have high volume fuel pump and pressure regulator no backfires

 

[Swims350]

need to check your timing and may also need to adjust the air fuel mixture if the screws are open to be able to adjust them, stock quads had caps not sure on the jet ones, but anyways need a timing light and a vacuum gauge, check the vac. gauge and set the mixture screws to get max. vac. and if that doesn't work check the timing.

It would be god to at least know where your timing is though before trying the carb tuning, because if the timing is off you'd want it right and then do the carb tweak.

 

[gpmorgan]

What kind of distributor do you have in it. That being a 402 and the last year they made it was 72 it would have points if it's still the original. I had a 72 402 that had a simular problem and ended up changing the dizzy(HEI) to get it to run right.

 

[86stepside]

timing is at 16 degrees tried setting carb and timing at different setting with no change

 

[86stepside]

changed to hei with 50,000 volt distributor about 6 months ago

 

[gpmorgan]

What pressure do you have the regulator set at? Why did you need the regulator? Is this a modified engine?

 

[86stepside]

new to this thanks for input but I keep losing my way in these boxes lol

 

[86stepside]

fuel pump puts out up to 14 lbs of pressure its set at 6 lbs its actually a 414 now but pretty much stock except cam has 218/224 @.50 527 lift

 

[gpmorgan]

Could you explain the symptoms a little more? Does it run ok when normal driving?

 

[86stepside]

normal driving it has a little off idle hesitation does great as long as i dont go past 3/4 throttle then it starts sputtering bad ease of throttle just a little and it levels off in park it works great no hesitation or high rpm sputter

 

[gpmorgan]

Have you tried turning the fuel pressure up? It sounds like it's not getting enough of a pump shot from the accellerator and mabe running out of fuel at higher rpms. Has it had this problem every since you rebuilt it? I have a 750 Holley running 6 1/2 lbs on the regulator. 355 sb
http://www.holley.com/VirtualShow/chevy/silverado/2607.asp

 

[86stepside]

no just started this about 3 week ago motor has beeen in truck for 7 months

 

[gpmorgan]

Is the choke in good working order? Choke pull off good? Sorry for all the questions.